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Australian fires 2019/20

January 12th, 2020 No comments

Australia is a very flammable continent, and fires have been occurring there for millions of years. As a consequence, many plants and animals have developed adaptations and strategies to cope with recurrent fires. However, the current fire season in eastern Australia is really very severe, including not only very large fires but also high intensity firestorms. SE Australia has suffered other sever fire seasons in the past (an iconic example is the Black Friday bushfires in 1939). Why is this happening now? Here I’ve compiled key figures that help us to understand it.

In the last few years, Australia has been suffering an increase in temperature; on average, each year is hotter than the previous year (Fig. 1). In fact, 2019 was the warmest years, but also the driest year (with the lowest rainfall) ever recorded. December 2019, when most fires started, was climatically an extreme (Fig. 2). During the December heatwave (Fig. 3) some meteorological station (e.g., Penrith, near Sydney) recorded temperatures over 48oC, and the record of highest average maximum temperature for Australia was broken on two consecutive days (40.7 and 41.9oC  on 17 and 18 Dec, respectively). January 4 was Canberra’s hottest day since records began (44oC). In such extreme weather conditions, ignitions easily become a wildfire (in fact, several of the wildfires started from a dry lightning), and fires spread very quickly in a vegetation that has been in a drought for many months. This makes not only huge areas burned (Fig. 4), but also generates very hot fires and strong uplift air columns that reach the stratosphere (pyrocumulonimbus). These are called firestorms. Firestorms produce there own winds and spread embers and the fire very fast; they even produce lightnings that generate more wildfires. Firestorms produce extreme fire behaviour that is beyond the capacity of firefighters. In those fires, as it happens in volcanoes, the smoke reaches the stratosphere and circulates at very long distances (e.g., currently smoke from these fires has already reached South America).

The fire season has not yet ended. The ecological effects of these fires will depend on many factors (spatial variability of fire intensity, previous fires, species, etc…). The size and intensity of the fires suggest that they can have some negative consequences, but it is too early for any quantitative evaluation. Many plants are starting to resprout just few days after the fire, even under those drought conditions; some animals are leaving their hiding places, exploring the burned area, and carcasses are locally abundant suggesting patches of high animal mortality. We’ll see when will the rain come, and how plants and animals will respond. For humans, the consequences are catastrophic (fatalities, destruction of many infrastructures, smoke problems, etc.).

Fig. 1. In Australia, each year is hotter than the previous year, on average. From Australian Bureau of Meteorology
Fig. 2. December 2019 was climatically an extreme, unprecedented in relation to rainfall and temperature. Elaborated with data from Australian Bureau of Meteorology
Fig. 3. Global temperature in December 18th, 2019, as shown by Windy. Note also that part of the differences in temperature are due to the different time zones; i.e., middle of the day in Australia, night time in South America, and early morning in Africa.
Fig. 4. Major fires in south-east Australia by January 10th, 2020 (5,634,000 ha). From @eforestal [update Jan 18th: 6 millions ha]

More information:

Australian Bureau of Meteorology  | @eforestal maphub  | NSW fire service | VIC emergency | Desinformation |

Alternative Biome States

January 8th, 2020 No comments

There is growing interest in the application of alternative stable state (ASS) theory to explain major vegetation patterns in tropical ecosystems [1] and beyond [2]. In a recent paper [3] we introduced the theory as applied to the puzzle of non-forested (open) biomes growing in climates that are warm and wet enough to support forests (alternative biome states, ABSs; Fig. 1). Long thought to be the product of deforestation, diverse lines of evidence indicate that many open ecosystems are ancient. They have also been characterized as ‘early successional’ even where they persist for millennia. ABS is an alternative framework to that of climate determinism and succession (Table 1 below) for exploring forest/nonforest mosaics. Within climatic and edaphic constraints, consumers (fire and herbivores) can produce vastly different ecosystems from the climate potential and have done so for millions of years [4]. This framework explains not only tropical forest–savanna landscapes, but also other landscape mosaics across the globe (Fig. 2).

Fig. 1. Generalized feedback processes in fire-prone landscapes where open and closed biomes (e.g., a grassland and forest) are alternative stable states maintained by stabilizing feedbacks, while perturbations generate abrupt transitions among states (destabilizing factors). From: [3].

Fig. 2. Examples of multibiome landscape mosaics where closed forests alternate with open biomes (grasslands) that are maintained by mammal herbivory and fire. From: [3].

Table 1. Comparison of the three main dynamic processes assembling disturbance-prone communities and landscapes: classical (facilitation) succession, autosuccession, and ABS. From: [3].

References

[1] Dantas V.L., Hirota M., Oliveira R.S., Pausas J.G. 2016. Disturbance maintains alternative biome states. Ecol. Lett. 19: 12-19. [doi | wiley | pdf | suppl.]

[2] Pausas, J.G. 2015. Alternative fire-driven vegetation states. J. Veget. Sci. 26:4-6. [doi | pdf | suppl.]

[3] Pausas J.G. & Bond W.J. 2020. Alternative biome states in terrestrial ecosystems. Trends Plant Sci. [doi | sciencedirect| pdf]

[4] Pausas J.G. & Bond W.J. 2019. Humboldt and the reinvention of nature. J. Ecol. 107: 1031-1037. [doi | jecol blog | jgp blog | pdf]  

Diversidad política (4)

January 7th, 2020 No comments

España es un país muy diverso, con una gran variedad de climas, paisajes, comidas, bailes, lenguas, hablas, etc.; una diversidad generada por su peculiar situación geográfica, su heterogeneidad topográfica y la variedad de acontecimientos ocurridos a lo largo de su historia. Esto ha conferido a la población una elevada diversidad cultural, de ideas y puntos de vista. Sólo un gobierno plural y diverso, capaz de aceptar las diferencias, podrá gestionar correctamente y preservar la diversidad de este país. El bipartidismo difícilmente puede representar la diversidad española.

En la figura (abajo) vemos la evolución de la diversidad política en España, calculado a partir la distribución de los escaños de los diferentes partidos (en azul), para todas las Elecciones Generales al Congreso realizadas durante la democracia. El 15M (mayo 2011) sirvió para revitalizar la diversidad política del Congreso, tras muchos años de decaimiento (ver figura, en azul).

Tras las últimas elecciones generales en noviembre de 2019, en España tenemos un Congreso con la mayor diversidad de ideas políticas de la historia de la democracia (ver figura, linea azul); y esperamos que sea capaz de gestionar bien la diversidad del país. La diversidad del Congreso es prácticamente la misma que después de las elecciones de abril de 2019 (como era esperable), y sin embargo, ese Congreso fue incapaz de gestionar esa diversidad, seguramente por la falta de experiencia democrática, es decir, falta de capacidad de diálogo, de capacidad para aceptar las diferentes opiniones, y de excesivo deseo de poder de los lideres. Esperemos que el nuevo Congreso, y el nuevo gobierno que ahora empieza, hayan aprendido la lección.

Cabe señalar que la diversidad de opciones políticas de los votantes españoles, calculadas a partir de los votos y las abstenciones (linea roja de la figura) es más elevada que la diversidad política que se refleja en el Congreso (escaños; linea azul). El sistema electoral español hace que se pierda un parte nada desdeñable de la diversidad política de los ciudadanos. Con la llegada del 15M se ha visto reducida esa pérdida de diversidad (la linea azul se acerca más a la roja). Aproximadamente el 30% de los censados decidieron no contribuir a confeccionar la composición del Congreso (abstenciones, votos en blanco, votos nulos), y por lo tanto, contribuyen a esa pérdida de diversidad en el Congreso. La figura también refleja que pequeños cambios de opinión en los votantes a lo largo del tiempo (linea roja) se reflejan de manera amplificada en el Congreso (linea azul).

Figura: Valores de diversidad política (expresada con el índice de diversidad de Shannon-Weaver) calculado a partir de las opciones de los votantes (incluye votos a partidos, blancos, nulos y abstención; en rojo) y calculado según la distribución de los escaños resultantes (azul), para cada una de las Elecciones Generales al Congreso (España) realizadas durante la democracia (elaborado a partir de la base histórica de resultados electorales del Ministerio del Interior).

Entradas relacionadas

Diversidad política (3): jgpausas.blogs.uv.es/2016/07/02/
Diversidad política (2): jgpausas.blogs.uv.es/2015/12/30/
Pérdida de diversidad política en España: jgpausas.blogs.uv.es/2008/03/11/ 
Carta a los no votantes: votar suma la abstención resta: jgpausas.blogs.uv.es/2019/04/13/

Nota aclaratoria: en las entradas previas sobre diversidad política en este blog, la diversidad política de los votantes (linea en rojo) se calculaba en base a la distribución de los votos a los distintos partidos. En esta entrada, y par reflejar un poco mejor la diversidad de las personas con derecho a voto, se ha calculado no sólo en base a los votos a los partidos, sino también incluyendo los votos en blanco, los nulos y las abstenciones.